The present invention relates to a technique effective to be applied to a PLL (Phase Locked Loop) circuit having a VCO (Voltage Controlled Oscillator) and capable of switching an oscillation frequency and further to a high-speed pull-in technique of a PLL circuit. More particularly, the invention relates to a technique effective to be applied to a PLL circuit for generating an oscillation signal of a predetermined frequency mixed with a reception signal or transmission signal in a radio communication device such as a portable telephone capable of transmitting/receiving signals in a plurality of bands, a semiconductor integrated circuit device for high frequencies having the same, and a radio communication system.
In a radio communication system such as a portable telephone, a PLL circuit is used as a local oscillator for generating an oscillation signal of a predetermined frequency mixed with a reception signal or transmission signal. Hitherto, there is a dual-band portable telephone capable of handling signals in two frequency bands of, for example, GSM (Global System for Mobile Communication) of a band from 880 to 915 MHz and a DCS (Digital Cellular System) of a band from 1710 to 1785 MHz. Some dual-band portable telephones can deal with two bands by a single PLL by switching the frequency of the PLL circuit.
In recent years, there is a demand for a triple-band portable telephone capable of handling signals of, in addition to the GSM and DCS, a PCS (Personal Communication System) of a band from 1850 to 1915 MHz. It is expected that a portable telephone capable of handling the larger number of bands will be requested in future.
For such a semiconductor integrated circuit device for high frequencies (hereinbelow, called RF IC) for modulating a transmission signal and demodulating a reception signal, which is used for a portable telephone adapted to a plurality of bands, a direct conversion method is effective from the viewpoint of reduction in the number of components. Although the direct conversion method is relatively easily adapted to a plurality of bands, the frequency range in which a VCO can oscillates is wide. If one VCO is used to cover the whole frequencies, the sensitivity of the control voltage of the VCO becomes high and it causes a problem such that the VCO becomes vulnerable to external noise and fluctuations in a power source voltage.
On the other hand, to reduce the number of components, it is effective to form a VCO, which is conventionally generally provided as a module separate from an RF IC, on the same semiconductor chip on which the RF IC is also mounted. However, in the case of forming a on-chip VCO, variations in the absolute value of an oscillation frequency increase for the reason of manufacture, so that the function of adjusting the oscillation frequency after manufacture becomes indispensable. In the case of adjusting the variations by trimming of general mask option or bonding wire option used for a conventional semiconductor integrated circuit, increase in cost cannot be avoided.